CN107112494B

CN107112494B - Battery, battery pack, electronic device, electric vehicle, power storage device, and power system

Info

Publication number: CN107112494B
Application number: CN201680003792.5A
Authority: CN
Inventors: 高桥秀俊; 三田和隆; 西山祥一
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Northeast China; Murata Manufacturing Co Ltd
Priority date: 2015-06-09
Filing date: 2016-06-02
Publication date: 2020-11-06
Anticipated expiration: 2036-06-02
Also published as: KR20180016329A; CN107112494A; WO2016199384A1; EP3309870B1; US20170301959A1; JP6384587B2; US10147973B2; EP3309870A4; JP2018170302A; JP2017152414A; JPWO2016199384A1; EP3309870A1; JP6729645B2; KR102122636B1; JP6791030B2

Abstract

The battery includes a positive electrode and a negative electrode, both continuously coated with an electrode mixture, wound and housed within an external element. The battery has a portion in which foil exposed surface sides of single-sided coating portions on outer sides of respective windings of the positive electrode and the negative electrode with an insulator therebetween are opposed to each other.

Description

Battery, battery pack, electronic device, electric vehicle, power storage device, and power system

Technical Field

The present technology relates to a battery, a battery pack, an electronic device, an electric vehicle, a power storage device, and a power system, in which an electrode to which an electrode composite material is applied is wound and housed in a laminate sheet exterior member.

Background

By reducing the proportion of components that are not involved in charging and discharging inside the battery pack, the energy density of the battery can be increased. However, if the thickness of the foil or separator is reduced, the safety against nail penetration is reduced. Therefore, in order to obtain a battery ensuring safety, the thickness of such a member needs to be maintained at a certain thickness or more.

Such a structure is provided: a positive electrode current collector and a negative electrode current collector on which an active material containing a coating film is not formed are disposed at the outermost periphery of a battery having a wound structure (hereinafter referred to as "wound foil structure") with a separator therebetween (for example, refer to patent document 1).

Reference list

Patent document

Patent document 1: japanese patent application laid-open No. H11-176478

Disclosure of Invention

Problems to be solved by the invention

The battery disclosed in patent document 1 is a cylindrical battery, and its structure is different from that of a battery covered with an external material such as a composite film. Also, when a battery of a wound foil structure is actually produced, safety is improved as compared with the case where the positive electrode current collector and the negative electrode current collector are not provided in the outermost periphery, but the volume of the current collector that does not contribute to charge and discharge increases in the outermost periphery, which leads to a problem of lower energy density.

An object of the present technology is to provide a battery, a battery pack, an electronic device, an electric vehicle, a power storage device, and a power system, which are capable of achieving higher energy density than a conventional wound foil structure while maintaining safety.

Solution to the problem

In order to solve the above-described problems, the present technology provides a battery in which a wound electrode element is wound around a positive electrode and a negative electrode with a separator interposed therebetween, wherein the positive electrode has a first exposed surface that is formed with a positive electrode active material layer on one surface of a positive electrode collector and is not formed with a positive electrode active material layer on the other surface of the positive electrode collector within an outer peripheral portion of the wound electrode element; the negative electrode has a second exposed surface that is in an outer peripheral portion of the wound electrode element, that is formed with a negative electrode active material layer on one surface of a negative electrode current collector, and that is not formed with a negative electrode active material layer on the other surface of the negative electrode current collector; and the first exposed surface and the second exposed surface are opposed across the separator.

The present technology provides a battery including a wound electrode element that is wound around a positive electrode and a negative electrode with a separator interposed therebetween, the positive electrode having a first exposed surface that is within an outer peripheral portion of the wound electrode element, a positive electrode active material layer being formed on one surface of a positive electrode collector, and no positive electrode active material layer being formed on the other surface of the positive electrode collector; and the first exposed surface is opposed to a region on both surfaces of the negative electrode current collector, on which the negative electrode active material layer is not provided, across the separator.

The present technology provides a battery including a wound electrode element that winds a positive electrode and a negative electrode across a separator, wherein the negative electrode has a second exposed surface that is within an outer peripheral portion of the wound electrode element, a negative electrode active material layer is formed on one surface of a negative electrode current collector, and no negative electrode active material layer is formed on the other surface of the negative electrode current collector; and the second exposed surface is opposed to a region on both surfaces of the positive electrode current collector, on which the positive electrode active material layer is not provided, across the separator.

A battery pack, an electronic device, an electric vehicle, a power storage device, and a power system of the present technology include the above battery.

Effects of the invention

According to at least one embodiment, since the back surface of the exposed surface of the current collector is coated with the electrode active material layer and thus has a function as a battery, the energy density is increased while securing safety. Note that the effects of the present technology are not limited to the effects set forth herein, but may include any effects mentioned in the present technology.

Drawings

FIG. 1 is a perspective view for explaining a battery to which the present technique is applied;

fig. 2 is a sectional view for explaining a wound electrode member;

FIG. 3 is an enlarged partial view of the wound electrode element;

fig. 4 is a sectional view for explaining one example of a conventional wound electrode member;

fig. 5 is a sectional view for explaining other examples of a conventional wound electrode member;

FIG. 6 is a cross-sectional view of one example of a wound electrode element to which the present technique is applied;

FIG. 7 is a cross-sectional view of another example of a wound electrode element to which the present technique is applied;

FIG. 8 is a graph of experimental results of energy density;

fig. 9 is a diagram of an experimental result of a nail penetration (nail penetration) allowable voltage;

FIG. 10 is a more detailed cross-sectional view of another example of a wound electrode element to which the present techniques are applied;

FIG. 11 is a more detailed cross-sectional view of another example of a wound electrode element to which the present techniques are applied;

fig. 12 is a sectional view for explaining a wound foil structure;

FIG. 13 is a sectional view for explaining a wound electrode member to which the present technique is applied;

fig. 14 is a schematic view for explaining the thickness of a conventional wound electrode member (normal structure);

fig. 15 is a schematic view for explaining the thickness of a conventional wound electrode element (wound foil structure);

FIG. 16 is a schematic view for explaining the thickness of a wound electrode member to which the present technique is applied;

FIG. 17 is a schematic view for explaining the thickness of a wound electrode member to which the present technique is applied;

fig. 18 is a perspective view for explaining electrode leads of a battery pack;

fig. 19 is a schematic view for explaining the length of an electrode lead wire inside a wound electrode member;

fig. 20 is a schematic view for explaining a position where electrode leads are provided;

fig. 21 is a schematic view for explaining the length of an electrode lead wire inside a wound electrode member;

fig. 22 is a sectional view for explaining an example of a wound electrode member;

fig. 23 is a sectional view for explaining an example of a wound electrode member;

FIG. 24 is a schematic diagram illustrating an example configuration for improving the safety against nail sticks;

fig. 25 is a schematic diagram showing an example configuration for suppressing short-circuit release;

fig. 26 is a schematic view for explaining a configuration in which two wound electrode members are accommodated in one external member;

fig. 27 is a schematic diagram showing a plurality of examples of the wire connecting method;

fig. 28 is a schematic diagram for explaining lead wire resistance between batteries in an example;

fig. 29 is a schematic diagram for explaining lead wire resistance between batteries in an example;

fig. 30 is a block diagram showing an example circuit configuration of a battery pack to which the present technology is applied;

fig. 31 is a schematic diagram showing a home electricity storage system to which the present technology is applied; and

fig. 32 is a schematic diagram schematically showing an example of the configuration of a hybrid vehicle using a series hybrid system to which the present technology is applied.

Detailed Description

The following is a description of embodiments of the present technology. It should be noted that the embodiments described below are preferred specific examples of the present technology with various technically preferable limitations; however, the scope of the present technology is not limited to these examples unless a specific limitation of the present technology is provided in the following description.

The present technology will be described in the following order.

<1, example of Battery >

<2, example of the present technology >

<3, application >

<4, modification >

<1, example of Battery >

An example of a composite thin-film battery to which the present technology is applied will now be described (for example, refer to japanese patent application laid-open No. 2001-266946). The present technology relates to a battery obtained by winding a positive electrode and a negative electrode in which electrode active material layers are seamlessly applied and accommodating the wound electrodes in an external element. Fig. 1 shows the configuration of a nonaqueous electrolyte battery 21. The nonaqueous electrolyte battery 21 includes a wound electrode member 10 contained inside a thin film exterior member 22 having an electrolyte (not shown).

The outer element 22 is made of a composite film having a metal layer and a plastic layer (on both sides of the metal layer). The composite film has an outer plastic layer formed on the surface of the metal layer exposed to the outside of the battery, and an inner plastic layer formed on the inner surface of the battery facing the power generating element (e.g., wound electrode element 10). The metal layer serves the most important function of preventing the intrusion of moisture, oxygen and light to protect the accommodated components, and is preferably made of aluminum (Al) or stainless steel for the reasons of light weight, ductility, low price and easy processing. For the outer plastic layer, a plastic material having good appearance, toughness, softness, etc., such as nylon or polyethylene terephthalate (PET) is used. Since the inner plastic layer has portions melted by heat or ultrasonic waves and bonded to each other, polyolefin resin is suitable for the inner plastic layer, and non-oriented polypropylene (CPP) is often used for the inner plastic layer. If necessary, adhesive layers may be provided between the metal layer and the outer plastic layer and between the metal layer and the inner plastic layer.

The outer element 22 has a recess for accommodating the wound electrode element 10, which recess is formed, for example, by deep drawing towards the inner plastic layer side of the outer plastic layer side, and the inner plastic layer is directed towards the wound electrode element 10. The mutually opposite inner plastic layers of the outer element 22 are bonded to each other at the outer edges of the recess by melting or the like. Adhesive films 23 are provided between the exterior element 22 and the positive electrode lead 16 and between the exterior element 22 and the negative electrode lead 17 to improve adhesion between the inner plastic layer of the exterior element 22 and the positive electrode lead 16 made of a metal material and between the inner plastic layer of the exterior element 22 and the negative electrode lead 17 made of a metal material.

One example of a wound electrode element 10 is now described with reference to fig. 2. Fig. 2 shows a cross-sectional structure along the line I-I of the wound electrode member 10 shown in fig. 1. The wound electrode element 10 is obtained by stacking the positive electrode 11 and the negative electrode 12 with the separator 15 therebetween and winding the resulting stacked structure. The outermost periphery of the resulting wound structure is protected with a protective tape, if necessary. The wound electrode member 10 has a structure formed by: stacking the positive electrode 11, the separator 15, and the negative electrode 12; winding the resulting stacked structure a plurality of times so that the area occupied by the wound electrode element 10 becomes small; and the resulting wound structure is compressed. The wound electrode element 10 also has an electrode lead (positive electrode lead) 16 as an internal main structure on the positive electrode side, an electrode lead (negative electrode lead) 17 on the negative electrode side, and

coating materials

18a, 18b, and 18 c.

The positive electrode 11 has a positive electrode collector 11a and positive electrode active material layers 11b formed on both surfaces of the positive electrode collector 11 a. Note that the positive electrode 11 may have a portion where the positive electrode active material layer 11b is formed on only one surface of the positive electrode collector 11 a. The positive electrode 11 is formed by coating a metal foil electrode (obtained by cutting a rolled aluminum foil into predetermined outer dimensions) with a positive electrode active material. A rolled aluminum foil is used because it has characteristics suitable for the positive electrode, such as good electrical conductivity and chemical properties, good winding processability, lightness and inexpensiveness.

The negative electrode 12 has a negative electrode current collector 12a and negative electrode active material layers 12b formed on both surfaces of the negative electrode current collector 12 a. Note that the negative electrode 12 may have a portion where the negative electrode active material layer 12b is formed only on one surface of the negative electrode current collector 12 a. The negative electrode 12 is formed by coating a metal foil electrode (obtained by cutting a rolled aluminum foil into a predetermined size) with a negative electrode active material for substantially the same reason as the above-described positive electrode 11.

The electrode lead 16 at the positive electrode side and the electrode lead 17 at the negative electrode side are both used to extract the electromotive force generated by the stacked structure to the outside. The electrode lead 16 is formed of a thin aluminum alloy plate or the like having good electrical conductivity and chemical reaction resistance inside the stacked structure.

As the electrolyte, a liquid electrolyte (i.e., an electrolytic solution), a gel electrolyte, or a solid electrolyte may be used. In the case where the electrolyte is an electrolytic solution, the inside of the exterior member 22 is filled with the electrolytic solution, and the wound electrode member 10 is impregnated with the electrolytic solution filled in the inside of the exterior member 22. In the case where the electrolyte is a gel electrolyte or a solid electrolyte, the electrolyte is provided between at least one of the positive electrode 11 and the negative electrode 12 and the separator 15. In this case, the wound electrode member 10 has the following structure: the positive electrode 11 and the negative electrode 12 are stacked with the separator 15 and a layer of electrolyte therebetween, and the resulting stacked structure is wound. In this case, the separator 15 may be omitted.

The electrolytic solution is, for example, a nonaqueous electrolytic solution containing a nonaqueous solvent dissolved in a solvent and an electrolyte salt. The gel electrolyte is gel-like, has electrochemical characteristics suitable for the electrolyte layer of each electrode, does not become liquid nor leak, and is resistant to bending and warping. Suitable electrolytes that meet this characteristic are, for example, electrolytes in which the electrolyte solution is homogeneously dispersed in the polymer matrix. The solid electrolyte is, for example, a solid polymer electrolyte having an ion-conductive polymer, a solid inorganic electrolyte having an ion-conductive inorganic material, or the like.

The separator 15 is made of a material that prevents electrical contact between the positive electrode 11 and the negative electrode 12, and allows ions to move sufficiently freely between the positive electrode 11 and the negative electrode 12, and microporous polypropylene or the like is suitable, for example.

The

coating materials

18a, 18b, and 18c provided at the respective positions are each made of an insulating material (e.g., an insulating polymer material) that electrically insulates the electrodes from each other even when the electrodes are brought close to each other by externally applying pressure to the stacked structure, or when there is a cutting burr at the end of the positive electrode collector 11a or the negative electrode collector 12 a. Further, the

coating materials

18a, 18b, and 18c have a thickness and a material having mechanical strength with which the

coating materials

18a, 18b, and 18c are not torn or broken even when one electrode is deformed by the application of such pressure and brought into contact with the other electrode. The

coating materials

18a, 18b, and 18c are formed by, for example, adhering adhesive insulating tapes such as adhesive tapes made of polyimide or polypropylene at respective positions.

Note that the coating material is not provided at the end to which the electrode lead 17 on the negative electrode 12 is connected. This is because, as shown in fig. 1, only the portions of the negative electrodes 12 are opposed to each other at the end portions with the separator 15 therebetween, and short-circuiting over such a short distance as can be ignored has little substantial adverse effect on the electromotive force of the battery.

Examples of the materials for the components of the battery as described above will be described in more detail.

[ Positive electrode active Material ]

For a positive electrode material capable of occluding and releasing lithium, for example, a lithium-containing compound is preferable. This is because a high energy density is achieved. Examples of the lithium-containing compound include a composite oxide containing lithium and a transition metal element and a phosphate compound containing lithium and a transition metal element. Among them, lithium-containing compounds containing at least one transition metal element selected from the group consisting of cobalt (Co), nickel (Ni), manganese (Mn), and iron (Fe)) are preferable. Because higher voltages are achieved.

Examples of the composite oxide containing lithium and a transition metal element include lithium cobalt composite oxide (Li)_xCoO₂) Lithium nickel composite oxide (Li)_xNiO₂) Lithium nickel cobalt composite oxidationSubstance (Li)_xNi_1-zCo_zO₂(z is more than 0 and less than 1)), and lithium nickel cobalt manganese composite oxide (Li)_xNi_(1-v-w)Co_vMn_wO₂(0 < v + w <1, v > 0, w > 0)), and a lithium manganese complex oxide (LiMn) having a spinel structure₂O₄) And lithium manganese nickel composite oxide (LiMn)_2-tNi_tO₄(0 < t < 2))). Among them, a composite oxide containing cobalt is preferable. This is because a high capacity is achieved and excellent cycle characteristics are achieved. In addition, examples of the phosphate compound containing lithium and a transition metal element include a lithium iron phosphate compound (LiFePO)₄) Or lithium manganese iron phosphate compound (LiFe)_1-uMn_uPO₄(0 < u)) and LixFe_1-yM2_yPO₄(in the formula, M2 represents at least one selected from the group consisting of manganese (Mn), nickel (Ni), cobalt (Co), zinc (Zn), and magnesium (Mg)); x represents a value in the range of 0.9. ltoreq. x.ltoreq.1.1.

In addition, examples of the positive electrode material capable of occluding and releasing lithium include oxides (e.g., vanadium oxide (V)₂O₅) Titanium dioxide (TiO)₂) And manganese dioxide (MnO)₂) Disulfide (e.g., iron disulfide (FeS)), disulfide₂) Titanium disulfide (TiS)₂) And molybdenum disulfide (MoS)₂) Chalcogenides (particularly layered compounds and spinel compounds) that are free of lithium (e.g., niobium diselenide (NbSe)₂) Lithium-containing compounds containing lithium, and conductive polymers such as sulfur, polyaniline, polythiophene, polyacetylene, or polypyrrole. Needless to say, the positive electrode material capable of occluding and releasing lithium may be different from the above. Further, two or more of the above-described positive electrode materials may be mixed in any combination.

[ negative electrode active Material ]

The negative electrode active material layer contains, as a negative electrode active material, any one or more of negative electrode materials capable of storing and releasing lithium, and may also contain other materials such as a binder and a conductive agent as necessary. In this case, the negative electrode material capable of storing and releasing lithium is preferably chargeable with a capacity greater than the discharge capacity of the positive electrode. Examples of the negative electrode material capable of occluding and releasing lithium include carbon materials. Examples of the carbon material include easily graphitizable carbon, (hardly graphitizable carbon with an interplanar spacing of (002) planes of 0.37nm or more, and graphite with an interplanar spacing of (002) planes of 0.34nm or less. More specifically, examples include pyrolytic carbon, coke, glassy carbon fiber, organic polymer compound fired bodies, activated carbon, and carbon black. Examples of the coke include pitch coke, needle coke, and petroleum coke, among others. The organic polymer compound fired body is a carbonized material obtained by firing a phenol resin, a furan resin, or the like at an appropriate temperature. The carbon material is preferable because the crystal structure thereof is little changed by lithium occlusion and release, thus realizing high energy density and excellent cycle characteristics, and further because the carbon material also functions as a conductive agent. Note that the shape of the carbon material may be any of a fiber, a sphere, a particle, and a scale.

Examples of the negative electrode material capable of occluding and releasing lithium include materials capable of occluding and releasing lithium and containing at least one of a metal element and a metalloid element as a constituent element, in addition to the above-described carbon material. Since a high energy density will be achieved. Such a negative electrode material may be a single metal element or metalloid element, an alloy thereof, or a compound thereof, or may partially contain a phase of one or more of the metal element and the metalloid element. Note that the "alloy" in the present invention includes an alloy containing one or more metal elements and one or more metalloid elements in addition to an alloy made of two or more metal elements. Further, "alloy" may contain a nonmetallic element. Examples of the structure thereof include a solid solution, a eutectic crystal (eutectic mixture), an intermetallic compound, and coexistence of two or more thereof.

Examples of the above-mentioned metal elements and metalloid elements include metal elements and metalloid elements capable of forming an alloy with lithium. Specifically, examples of the metal elements and metalloid elements include magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd), and platinum (Pt). Among these, at least one of silicon and tin is preferable, and silicon is more preferable. This is because these elements can efficiently absorb and release lithium, and thus achieve a high energy density.

Examples of the negative electrode material having at least one of silicon (Si) and tin (Sn) include a single silicon element, an alloy thereof and a compound thereof, a single tin element, an alloy thereof and a compound thereof, and the material partially contains one or more phases of the material.

Examples of the silicon alloy include an alloy containing at least one selected from the group consisting of tin (Sn), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr) as a second constituent element other than silicon.

Examples of the tin alloy include alloys containing, as a second constituent element other than tin (Sn), at least one selected from the group consisting of silicon (Si), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr).

Examples of the tin compound and the silicon compound include compounds containing oxygen (O) or carbon (C), and may contain the above-described second constituent element in addition to tin (Sn) or silicon (Si).

In particular, as for a negative electrode material containing at least one of silicon (Si) and tin (Sn), for example, a material containing tin (Sn) as a first constituent element and also containing a second constituent element and a third constituent element in addition to tin (Sn) is preferable. Needless to say, the negative electrode material may be used together with the above-described negative electrode material. The second constituent element is at least one selected from the group consisting of cobalt (Co), iron (Fe), magnesium (Mg), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), zirconium (Zr), niobium (Nb), molybdenum (Mo), silver (Ag), indium (In), cerium (Ce), hafnium (Hf), tantalum (Ta), tungsten (W), bismuth (Bi), and silicon (Si). The third constituent element is at least one selected from the group consisting of boron (B), carbon (C), aluminum (a1), and phosphorus (P). This is because the cyclic characteristics are improved by the second element and the third element contained therein.

Among them, the following CoSnC-containing material (containing tin (Sn), cobalt (Co), and carbon (C) as constituent elements) is preferable: wherein the content of carbon (C) is in the range of 9.9 to 29.7% by mass, and the ratio of cobalt (Co) to the sum of (Sn) and cobalt (Co) (Co/(Sn + Co)) is in the range of 30 to 70% by mass. This is because high capacity is achieved and excellent cycle characteristics are achieved within these composition ranges. The SnCoC-containing material may further contain another constituent element as necessary.

As for the other constituent elements, for example, silicon (Si), iron (Fe), nickel (Ni), chromium (Cr), indium (In), niobium (Nb), germanium (Ge), titanium (Ti), molybdenum (Mo), aluminum (a1), phosphorus (P), gallium (Ga), and bismuth (Bi) are preferable, and two or more thereof may be contained. This is because the capacitance characteristic or the cycle characteristic will be further improved. Note that the SnCoC-containing material preferably has a phase containing tin (Sn), cobalt (Co), and carbon (C), and the phase preferably has a low crystalline structure or an amorphous structure. Further, in the SnCoC-containing material, at least a part of carbon as a constituent element is preferably bonded to a metal element or a metalloid element as another constituent element. This is because the reduction in cycle characteristics is considered to be caused by aggregation or crystallization of tin (Sn) or the like, and such aggregation or crystallization can be reduced by binding carbon to other elements.

[ Binders ]

The adhesive comprises, for example, any one or more of a synthetic rubber, a polymeric material, and the like. Examples of synthetic rubbers include styrene-butadiene rubber, fluororubber, and ethylene propylene diene. Examples of polymeric materials include polyvinylidene fluoride and polyimide.

[ conductive agent ]

The conductive agent contains, for example, any one or more of carbon materials and the like. Examples of the carbon material include graphite, carbon black, acetylene black, and ketjen black. Note that the conductive agent may be a conductive metal material, a conductive polymer, or the like.

[ separator ]

The separator has a function of separating the positive electrode and the negative electrode from each other and allowing lithium ions to pass therethrough while preventing a current short circuit caused by contact between the electrodes, and may be made of synthetic resin, ceramic, or the like. In addition, in order to ensure the safety of the lithium ion battery, the separator may have a shut-down function. The shutdown function as used herein refers to a function of shutting off pores of the microporous membrane to shut off current when the temperature of the battery increases, which serves to prevent thermal runaway of the battery. Examples of materials having all of these functions include polyolefins and microporous polyethylene films.

Depending on the design of the battery, the temperature of the battery after shutdown may become further high, the separator may melt, and a short circuit may occur in the battery, resulting in smoke, fire, and the like. Therefore, there have been proposed techniques of coating one surface or both surfaces of a microporous polyethylene film with a heat-resistant porous layer, stacking a nonwoven fabric layer made of heat-resistant fibers on one surface or both surfaces, and incorporating ceramic powder into these layers. For example, a nonaqueous electrolyte battery separator in which a heat-resistant porous layer made of a heat-resistant polymer such as aromatic aramid, polyimide, or polyvinylidene fluoride is stacked on one surface or both surfaces of a microporous polyethylene film by a wet coating method is well known, and the separator can be used. For example, to form the polymer compound layer, the base layer may be coated with a solution in which a polymer material is dissolved and then dried, or the base layer may be immersed in the solution and then dried.

[ electrolyte ]

The electrolytic solution contains a solvent and an electrolyte salt.

Examples of the solvent include Ethylene Carbonate (EC), Propylene Carbonate (PC), butylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methylpropyl carbonate, γ -butyrolactone, γ -valerolactone, 1, 2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1, 3-dioxolane, 4-methyl-1, 3-dioxolane, 1, 3-dioxane, 1, 4-dioxane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, trimethyl acetate, trimethyl ethyl acetate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N-dimethylformamide, N-methylpyrrolidone, N-methyloxazolidinone, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methylpropyl carbonate, gamma-butyrolactone, dimethylvaleronitrile, 1, 3-dioxolane, 1, 4-dioxane, methyl acetate, methyl propionate, methyl, N, N' -dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate and dimethyl sulfoxide. This is because when the electrolytic solution is used in an electrochemical device such as a battery, excellent capacity, cycle characteristics, and storage characteristics are achieved. These solvents may be used alone, or two or more thereof may be used in combination. Among them, the solvent is preferably a solvent containing at least one selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. This is because a sufficient effect is produced. In this case, a solvent containing a mixture of ethylene carbonate or propylene carbonate (a high-viscosity (high dielectric constant) solvent) (e.g., a relative dielectric constant r.gtoreq.30) and dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate (a low-viscosity solvent (e.g., viscosity. ltoreq.1 mPas)) is particularly preferable. This is because the dissociation of the electrolyte salt and the mobility of the ions will increase, thus producing a greater effect. Note that the solvent may be a material other than the above-described materials.

The electrolyte salt contains, for example, one or more light metal salts, for example, lithium salts. Examples of the lithium salt include lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate (LiBF)₄) Lithium perchlorate (LiClO)₄) Lithium hexafluoroarsenate (LiAsF)₆) Lithium tetraphenylborate (LiB (C)₆H₅)₄) Lithium methanesulfonate (LiCH)₃SO₃) Lithium trifluoromethanesulfonate (LiCF)₃SO₃) Lithium aluminum tetrachloride (LiAlCl)₄) Lithium hexafluorosilicate (Li)₂SiF₆) Lithium chloride (LiCl) and lithium bromide (LiBr). Among them, at least one selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate and lithium hexafluoroarsenate is preferable, and lithium hexafluorophosphate is more preferable. This is because the resistance of the electrolyte decreases. Note that the electrolyte salt may be a material other than the above-described materials.

Alternatively, a solution obtained by gelling the above electrolytic solution with a matrix polymer may be used. The matrix polymer may be any matrix polymer that is compatible with an electrolytic solution obtained by dissolving an electrolyte salt in a solvent and can be gelled. Examples of such matrix polymers include polymers comprising vinylidene fluoride (VdF), Ethylene Oxide (EO), Propylene Oxide (PO), Acrylonitrile (AN), or Methacrylonitrile (MAN) as repeating units. A single polymer of such polymers may be used alone, or two or more thereof may be used in combination. The gel electrolyte is preferable because high ionic conductivity (e.g., 1mS/cm or more at room temperature) is achieved and leakage is prevented. Further, the electrolytic solution may contain a metal oxide.

Next, an outline of a method for manufacturing a lithium ion secondary battery will be explained, focusing on a process of forming a coating material and a process of applying a pressing force to the stacked structure.

As described above, the positive electrode 11 having the electrode application portion to which the gel electrolyte is applied, the separator 15, and the negative electrode 12 having the electrode application portion to which the gel electrolyte is applied are stacked, the electrode lead 16 on the positive electrode side is connected to the positive electrode 11, and the electrode lead 17 on the negative electrode side is connected to the negative electrode 12, thereby forming a stacked structure having a flat shape before winding.

Then, before spirally winding the stacked structure, a coating material 18a is adhered to a part of the collector exposed surface (facing the negative electrode collector) of the end portion of the positive electrode 11, the coating material 18a is made of an insulating tape such as polyethylene terephthalate (PET), polypropylene (PP), or Polyimide (PI) to cover the surface of the electrode lead 16 on the positive electrode side, and the coating material 18a has insulation and mechanical strength. Meanwhile, a coating material 18b is bonded, the coating material 18b being made of an insulating tape such as polyethylene terephthalate (PET), polypropylene (PP), or Polyimide (PI) to cover a current collector exposed surface of a portion of the end of the negative electrode 12 (a current collector exposed portion facing on the positive electrode inner peripheral portion). Note that the inner peripheral portion used in the present technology refers to a region located in the vicinity of one end in the longitudinal direction of each electrode closer to the center of the wound electrode element, and the outer peripheral portion refers to a region located in the vicinity of the other end in the longitudinal direction of each electrode closer to the outer element.

After bonding the

coating materials

18a, 18b, and 18c in this manner, the stacked structure is wound into a relatively flat spiral shape, and further pressing force is applied thereto on the outside, so that the stacked structure becomes flatter and thinner. In this process, even when one end of the positive electrode 11 and the negative electrode 12 are brought closer to each other or one end of the negative electrode 12 and the positive electrode 11 are brought closer to each other due to the application of the pressing force, the

coating materials

18a, 18b, and 18c prevent the electrodes from contacting each other and causing an electrical short circuit. In the case of using a gel electrolyte, hot pressing may be subsequently performed as a process of impregnating the positive and negative electrodes and the separator with the electrolyte. In the case of using a liquid electrolyte, the electrolyte may be injected after inserting the flat thin element into the laminate.

<2, example of the present technology >

The present technique improves safety without reducing energy density. The present technique will now be described with reference to the accompanying drawings. For the sake of simplicity, the diagram of winding the electrode element shows collectors at the outer peripheries that are different in structure, and shows the application of the positive electrode active material layer 11b to the positive electrode 11 of the positive electrode collector 11a and the application of the negative electrode active material layer 12b to the negative electrode 12 of the negative electrode collector 12a, as shown in fig. 3. The separators, protective tape, and structures on the inner periphery will not be shown except in some of the drawings.

Fig. 4 shows an example of a winding structure (normal structure) for comparison. In this structure, a part of the negative electrode, in which the active material layer is formed on only one surface, exists only in the inner peripheral portion, a part of the positive electrode, in which the active material layer is formed on only one surface, exists only in the outer peripheral portion, and there is no portion where the collector exposed surfaces of the positive electrode and the negative electrode face each other (with the separator therebetween), except for a portion necessary for connecting the electrode lead. When using this normal configuration, the occupation of the current collectors in the cell is substantially minimal.

Fig. 5A and 5B show other examples of winding structures (wound foil structures) for comparison. The wound foil structure corresponds to the structure of patent document 1 described at the beginning configured for use in a battery having an exterior material of a composite film. Fig. 5B shows a part of the structure in fig. 2 of patent document 1. The wound foil structure is a structure in which the positive electrode collector 11a and portions of the negative electrode collector 12a whose both surfaces are free of the active material layers are disposed adjacent to each other at the outermost periphery. In the case of such a structure, safety is improved as compared with the case where the positive electrode collector and the negative electrode collector are not provided at the outermost peripheral portion, but the volume of the collector that does not contribute to charge and discharge is increased within the outermost peripheral portion, which leads to a problem of lower energy density.

Fig. 5B shows a detail of the outermost periphery of the electrode member having a wound structure and its vicinity. In fig. 5B, 1 denotes a sheet-like positive electrode, and 2 denotes a sheet-like negative electrode. The positive electrode 1 is produced by forming active material layers 1b on both surfaces of the positive electrode collector 1 a. The negative electrode 2 is produced by forming active material layers 2b on both surfaces of the negative electrode current collector 2 a. Then, the positive electrode 1 and the negative electrode 2 are spirally wound (with the separator 3 therebetween), and accommodated in the battery can 5 as an electrode element having a spirally wound structure with an electrolytic solution. At the outermost periphery of the positive electrode 1, there is provided a portion: the active material layer 1b is not formed on each surface, and only a portion of the positive electrode collector 1a is present. Also, at the outermost periphery, there is provided a portion: wherein the active material layer 2b is not formed, and only a portion of the negative electrode current collector 2a is present. In the structure shown in fig. 5B, the active material layer 2B is also present on the outside of a portion thereof facing the negative electrode 2 of the positive electrode collector 1a (which is not used as a battery). Thus, the energy density of the structure of fig. 5B is further lower than the wound foil structure shown in fig. 5A.

Fig. 6 shows a first example of a winding structure of the present technology (referred to as a single-sided foil-foil structure (1)). The single-sided foil-foil structure (1) is a structure in which the collector-exposed portion of the single-sided application portion of the negative electrode 12 faces the positive electrode collector 11a of the positive electrode 11, as shown in the dotted circle. Specifically, the single-sided foil-foil structure (1) is a battery: the collector exposed surface having the single-sided application portion on the outer side of the winding of either of the positive electrode and the negative electrode faces the portion of the collector of the other electrode with the insulator (separator) therebetween.

Fig. 7 shows a second example of a winding structure of the present technology (referred to as a single-sided foil-foil structure (2)). The single-sided foil-foil structure (2) is a structure in which the foil collector exposed portion of the single-sided application portion of the positive electrode 11 faces the collector exposed portion of the single-sided application portion of the negative electrode 12, as shown in the dotted circle. Specifically, the single-sided foil-foil structure (2) is a battery having portions opposing each other on the collector exposed surface sides of the single-sided application portions outside the windings of the positive and negative electrodes.

Thus, the mechanism of improved safety of the stapled wound foil structure compared to the normal structure has been analyzed. As a result, it was found that:

1. since a low-resistance short circuit occurs at a portion where the positive electrode collector and the negative electrode collector oppose each other, the amount of heat generation at a portion where the electrode application portions oppose each other is reduced; and

2. when the portion where the positive electrode collector and the negative electrode collector oppose each other is provided at the outermost peripheral portion, the amount of heat generation at the portion where the electrode application portions oppose each other starts to decrease from the time of nail penetration.

The synergistic effect of the above two effects makes it less likely that the battery will suffer thermal runaway.

Further, it has been found that the current path at the portion where the positive electrode collector and the negative electrode collector oppose each other is mainly on the path where the positive electrode collector and the negative electrode collector directly contact each other, not on the path where the positive electrode collector and the negative electrode collector are short-circuited by nails.

These results indicate that the metal surfaces of both surfaces of the positive electrode collector and the negative electrode collector need not be exposed, and the surfaces of the metal surfaces that oppose each other need only be provided at the outer peripheral portion.

Therefore, what the structure in which the metal surfaces as current collectors face each other on the outer peripheral portion of the battery may be has been studied, and the battery has actually been produced so that the relationship between the thickness and the safety will be clarified.

Fig. 8 and 9 are diagrams illustrating experimental results of the normal structure, the wound foil structure, the single-sided foil-foil structure (1), and the single-sided foil-foil structure (2) illustrated in fig. 4 to 7, respectively. The plots in the figure are based on the experimental results shown in table 1 below. In one example, aluminum (a1) is used for the positive electrode collector 11a and copper (Cu) is used for the negative electrode collector 12 a.

Note that since the size of table 1 is large, it is divided into 4 in the vertical direction and the horizontal direction. The upper left portion of table 1 is table 1A, the upper right portion of table 1 is table 1B, the lower left portion of table 1 is table 1C, and the lower right portion of table 1 is table 1D. Further, in each table obtained by the division, the leftmost field on each row (examples 1 to 20, comparative examples 1 to 11, structure name) and the uppermost field on each column ("there are a portion where collectors oppose each other", "thickness [ μm ] of positive electrode collector", and "warp [ μm ] at full charge") are added.

The following parameters in the uppermost fields of the columns in table 1 are described below:

"height of electrode element", "length of positive electrode lead within electrode element", "length of negative electrode lead within electrode element", "P_CL”、“P_CR”、“P_AL”、“P_AR"," width of electrode element ", and" X_L”、“X_R”、“Y_L”、“Y_R"," warp when filled ".

The graph shown in fig. 8 shows the change in the volumetric energy density when the thicknesses of aluminum (a1) as the positive electrode current collector, copper (Cu) as the negative electrode current collector, and a separator (SEPA.) are reduced in each of examples 1 to 5 (single-sided foil-foil structure (1)), examples 6 to 10 (single-sided foil-foil structure (2)), comparative examples 1 to 5 (normal structure), and comparative examples 6 to 10 (wound foil structure). The diagram of fig. 8 shows that the single-sided foil-foil structure (1) and the single-sided foil-foil structure (2) to which the present technique is applied have an intermediate energy density between that of the wound foil structure and the normal structure.

The graph shown in fig. 9 shows the relationship between the volumetric energy density and the nail penetration permitting voltage when the thickness of the part does not contribute to charging and discharging in each of the single-sided foil structure (1), the single-sided foil structure (2), the normal structure, and the wound foil structure. Note that the single-sided foil-foil structure (1) corresponds to examples 1 to 5, the single-sided foil-foil structure (2) corresponds to examples 6 to 10, the normal structure corresponds to comparative examples 1 to 5, and the wound foil structure corresponds to comparative examples 6 to 10. The nail penetration permitting voltage refers to a voltage charged before the nail penetration test, and no gas is ejected at the time of the nail penetration test. Fig. 9 is a graph showing that the nail penetration allowable voltage of the single-sided foil-foil structure (1) and the single-sided foil-foil structure (2) to which the present technique is applied is higher than that of the normal structure and the wound foil structure when compared with the same volumetric energy density; namely, the single-sided foil-foil structure (1) and the single-sided foil-foil structure (2) achieve higher safety while maintaining higher energy density.

Note that the nail penetration permitting voltage in table 1 is obtained as follows. Batteries having different charging voltages at different levels are provided. In examples 1 to 10 and comparative examples 1 to 10, a nail having a diameter of 2.5mm was inserted into the central portion of each battery at a speed of 100 mm/sec. Thereafter, if the laminate sheet bursts and the gas is sprayed at a suddenly increased temperature, the battery is determined to be an NG battery. The test was performed on five cells from both sides at a certain voltage. If none of the batteries is determined to be NG, the voltage is determined as the nail penetration permitting voltage in the corresponding specification. In examples 11 to 14, 19 and 20 and comparative example 11, nails were insertedThe position is not the center part of the battery but is moved only in the width direction of the battery by (Y)_L+Y_R) The position of the calculated quantity and the nail stick allowed voltage is checked as above. For example, in the case of example 12, since Y_L-30 and Y_RAnd-2, so the nailing was performed only at a position shifted from the center of the battery ((-30+ (-2)/2) —)16 in the width direction.

Further, the thickness of the battery during charging in table 1 is defined as the thickness measured by sandwiching the battery with two metal plates that change the spacing between the surfaces while keeping the two metal plates parallel to each other.

As described above, it has been found that the one-sided foil-foil structure (2) shown in fig. 7) having a portion where the collector exposed surface sides of the one-sided application portions on the outer peripheral portions of the positive and negative electrodes are opposed to each other and the one-sided foil-foil structure (1) (fig. 6) having a portion where the collector exposed surface of the one-sided application portion on the outer peripheral portion of either one of the positive and negative electrodes and the collector of the other electrode are opposed to each other with an insulator (separator) therebetween are structures which no longer have the relationship between the safety and the energy density obtained in the normal structure and the wound foil structure but can achieve a higher energy density while maintaining the safety. Note that the results of energy density and safety shown in fig. 9 are only results obtained by a combination of the materials used in the examples and the size of the fabricated battery. Therefore, in the case of manufacturing a battery using another thermal stability material and having a battery size in which temperature does not easily rise, it is possible to achieve a higher energy density while maintaining high safety by using thin members in combination.

Among them, it has been found that particularly high safety (examples 6 to 10) can be achieved in the case of a single-sided foil-foil structure (2) in which a portion where one layer of a positive electrode and one layer of a negative electrode are opposed to each other is provided outside a portion where exposed surface sides of collectors of single-sided application portions on outer circumferential portions of the positive electrode and the negative electrode are opposed to each other. As a result of the fracture and observation of the battery after penetration, the reason why the safety of the single-sided foil-foil structure (2) is high is considered as follows: since the position of the foil to the foil opposing portion (the portion where the collector exposed surface sides of the positive and negative electrodes oppose each other) is distant from the external element, catching the external element is less likely to cause suppression of short-circuiting of the foil to the foil opposing portion; and since the exposed portions of the foil current collectors applied to the sides of the positive and negative electrodes are opposed to each other to form the foil-to-foil opposed portions, elimination of short circuits (release) due to melting of the current collectors at the time of heat generation is less likely to occur, as compared with the case where only the current collectors are formed separately to the foil-to-foil opposed portions.

Note that the foil-to-foil opposing portion need not cover the entire surface in the cell, but may be provided in part. The purpose in this case will be explained.

First, as for the surface on which the foil-to-foil opposing portion is provided, providing the foil-to-foil opposing portion on the outer peripheral portion is very effective for improving safety. Therefore, if external damage is expected to occur only on one side of the surface, it is desirable to: providing the foil on the outside of the surface to the opposite part of the foil will improve the security. Further, since the effect is more likely to be maintained as the number of foil-to-foil opposing portions increases, the foil-to-foil opposing portions may be provided on the surfaces on the side subject to external damage and the other side for further improving safety.

Further, depending on the use of the battery and the location of the battery in the device, there are cases where the penetration safety needs to be improved only in one portion such as "the left half portion of the battery" or "only the middle portion". Alternatively, depending on the internal structure, there are cases where: at the time of nail sticking, there are portions with high safety and portions with low safety. In these cases, an incentive arises to provide foil to foil opposing portions only on one portion of the peripheral portion.

In the case of a wound battery, measures are taken to generate electricity with high reliability whenever the electrode portion is converted into a collector-exposed portion. The first measure is to apply the positive electrode active material layer longer than the negative electrode active material layer, and the second measure is to cover the end of the positive electrode application with an adhesive tape. These measures consume additional volume, reducing the energy density. Therefore, in view of energy density, each of the positive electrode and the negative electrode is preferably formed of a seamless electrode application portion within one wound electrode element.

Fig. 10 shows a single-sided foil-foil structure (2) in which a coating material (protective tape) 18a is provided so as to cover from the application starting end of the positive electrode active material that contains the coating film 11b and includes the lead-out portion of the positive electrode lead 16, the coating material (protective tape) 18b is provided on the negative electrode collector 12a toward the cut end of the positive electrode collector 11a, and a coating material (protective tape) 18c is provided at a position where the positive electrode active material containing the coating film 11b is switched from double-sided application to single-sided application.

Fig. 11 shows a single-sided foil-foil structure (2) in which a protective tape 18c is provided over the entire outer peripheral portion from the position where the positive electrode active material containing the coating film 11b is switched from double-sided application to single-sided application. Either of the structures of fig. 10 and 11 may be used.

For example, in the wound foil structure shown in fig. 12, in order to improve the penetration safety of the range a surrounded by the dotted line, the foil is started from the position B to the foil opposing portion, so that safety and energy density can be achieved. In fig. 12, X' represents a length from the foil to the start of the foil opposing portion to the start of the bent portion when the electrode is viewed from the inner peripheral portion toward the outer peripheral portion. Y' represents a length from an end of the bent portion (start of the flat portion) to an end of the foil-to-foil opposing portion when the electrode is viewed from the inner peripheral portion toward the outer peripheral portion.

In the case of the single-sided foil-foil structure (2) shown in fig. 13, in order to improve the penetration safety of the range a enclosed by the broken line, the foil is started from the position B to the foil opposing portion, thereby achieving the object. Portions of the exposed surfaces of the foils opposite to each other are present on both surfaces of the cell, wherein the length from the foil to the beginning of the foil opposite portion to the corner of the bent portion is defined as X, and the length from the corner of the bent portion to the end of the foil-foil opposite portion is defined as Y. In this case, it has been found that when the lengths X and Y are changed, the resulting capacity retention rate after charge-discharge cycles is also changed. This will be described below.

After repeating 1-C charge (CC (constant current)/CV (constant voltage) for 4.35V, (1/20) C cut-off) and 1-C discharge (CC discharge, 3V cut-off) for 200 cycles, the discharge capacities of the respective structures were compared, and as a result, the battery having a single-sided foil-foil structure and a size (X.gtoreq.Y) had the highest retention rate (retentivity).

Due to the reason that the battery is decomposed and inspected after the cycle is performed to determine the result, lithium is mainly locally precipitated to a bent portion or the like in the battery having a low cycle retention rate, and the thickness of the battery increases. This is considered to have triggered the reduction of the cycle retention rate.

A process of pressing in a plane direction to stabilize the shape of the battery may be performed after winding the electrodes. However, in this case, the structure of precipitating lithium (Li) to the bent portion is a structure in which the pressure is unlikely to be applied unevenly to the entire surface at the time of pressing, and the pressure applied to the bent portion is uneven

Fig. 14 shows the thickness of the battery in the case of the normal structure (comparative example 2). In the case of the normal structure, since the pressure applied around the bent portion in the winding structure is uniform as indicated by the dotted circle, the thickness obtained by pressing is also uniform.

Fig. 15 shows the thickness of the battery in the case of winding the foil structure (half turn) (comparative example 7). In the case of the wound foil structure, since the pressure applied around the bent portion in the wound structure is not uniform as indicated by the dotted circle, the thickness obtained by pressing is also not uniform.

Fig. 16 shows the thickness of the cell in the case of a single-sided foil-foil structure (example 11, Y < X). In the case of the wound foil structure, since the pressure applied around the bent portion in the wound structure is uniform as indicated by the dotted circle, the thickness obtained by pressing is also uniform.

Fig. 17 shows the thickness of the battery in the case of a single-sided foil-foil structure (example 13, Y > X). In the case of the wound foil structure, since the pressure applied around the bent portion in the wound structure is not uniform as indicated by the dotted circle, the thickness obtained by pressing is also not uniform.

As described above, it is considered that in the battery having the single-sided foil-foil structure and the size (Y < X), since the thickness around the bent portion is uniform, the pressing pressure is uniformly applied, the precipitation of lithium Li around the bent portion is suppressed, and the cycle retention rate is thus increased.

Further, also in terms of energy density, since the thickness distribution of the battery is more uniform, the size of (Y < X) is preferable, and it is more preferable to set Y as close to X as possible.

Next, measures for battery warping are described. Fig. 18 shows an external view of the battery 21. The positive electrode lead 16 and the negative electrode lead 17 are drawn from the external element 22. These leads have a thickness in the range of 70[ mu ] m to 100[ mu ] m, and are connected to a current collector exposed portion provided at the inner peripheral portion of a wound electrode element (referred to as an electrode element where appropriate). The width H of the negative electrode in the wound electrode element (referred to as an electrode element, where appropriate) housed in the external element 22 is referred to as the height [ mm ] of the electrode element (see table 1). Further, the width W of the surface from which the lead is drawn out is referred to as the width [ mm ] of the electrode member (see table 1). Further, the lengths L of the positive electrode lead 16 and the negative electrode lead 17 inserted into the wound electrode element (referred to as an electrode element, where appropriate) housed in the exterior element 22 are referred to as the length [ mm ] of the positive electrode lead inside the electrode element and the length [ mm ] of the negative electrode lead inside the electrode element, respectively (see table 1).

Fig. 19A shows the height H of the electrode element and the length L of the negative electrode lead within the electrode element with respect to the cross section of the battery 21. In the cross section of the battery 21, as shown in fig. 19B, the positive electrode 11 and the negative electrode 12 are stacked with the separator 15 therebetween. Fig. 19A and 19B show the configuration related to the negative electrode lead 17, and the configuration of the positive electrode lead 16 is similar thereto.

In the battery 21, the warpage is caused by a combination of factors such as the balance of the number of layers above and below the start of the winding as a center and the repulsive force received by the electrode elements from the external element. The degree of curvature of the warp is large around the center of the battery. As shown in fig. 20A, when the lengths of the positive electrode lead and the negative electrode lead within the electrode element are both equal to or less than half (H/2) of the height H of the electrode element, warpage cannot be suppressed. As shown in fig. 20B, when at least one of the lengths of the positive electrode lead and the negative electrode lead within the electrode element is larger than half (H/2) of the height H of the electrode element, warping can be suppressed. Therefore, warping is effectively suppressed by the presence of the rigid metal plate such as the lead wire around the center of the battery.

The definition of warping will be explained. The thickness measured by sandwiching the cell between two flat plates that are movable in parallel is denoted by a, and the thickness value at the center of the top surface of the cell measured by placing the cell on a surface plate such that one face of the cell faces downward and using a thickness measuring device having a hemispherical tip with a diameter of 3mm is denoted by B1. The thickness value at the center of the top surface of the cell measured by placing the cell on the surface plate so that the top and bottom surfaces are opposite to those of the cell used for measuring B1 and in a manner similar to B1 is represented by B2. The difference between the value of the smaller of B1 and B2 and the value a is defined as the amount of warpage. For the measurement, the probe or plate is pressed against the cell with a force of 1.5N. If the warpage occurs, the value a increases in addition to the pure thickness of the battery. If it is attempted to store the battery in the space of the rectangular parallelepiped, this means that the volume of the rectangular parallelepiped increases, having the same capacity but the energy density becomes smaller.

The above table 1 includes data of "height of electrode element", "length of positive electrode lead inside electrode element", "length of negative electrode lead inside electrode element", and "warp at full charge". For example, in example 10, the length of the positive electrode lead inside the electrode element and the length of the negative electrode lead inside the electrode element were both 20[ mm ] with respect to the height (70[ mm ]) of the electrode element. Since the length is smaller than 1/2(35[ mm ]) which is the height of the electrode element, warpage (80[ μm ]) at the time of filling occurs.

Example 15 is different from example 10 in that the length of the positive electrode lead inside the electrode element and the length of the negative electrode lead inside the electrode element are both 30[ mm ]. Since this value is also smaller than 1/2(35[ mm ]) which is the height of the electrode element, warpage (80[ μm ]) at the time of filling occurs.

Example 16 differs from example 10 in that the length of the positive electrode lead inside the electrode element and the length of the negative electrode lead inside the electrode element were both 40[ mm ]. Since this value is larger than 1/2(35[ mm ]) of the height of the electrode element, the warpage at the time of filling is suppressed to (20[ μm ]).

Example 17 differs from example 10 in that the length of the positive electrode lead inside the electrode element was 20[ mm ], and the length of the negative electrode lead inside the electrode element was 40[ mm ]. Since the length of the negative electrode lead inside the electrode element is greater than 1/2(35[ mm ]) the height of the electrode element, the warpage at the time of filling is suppressed to (20[ μm ]).

Example 18 differs from example 10 in that the length of the positive electrode lead inside the electrode element was 40[ mm ], and the length of the negative electrode lead inside the electrode element was 20[ mm ]. Since the length of the positive electrode lead inside the electrode element is greater than 1/2(35[ mm ]) the height of the electrode element, the warpage at the time of filling is suppressed to (20[ μm ]). As described above, if at least one of the length of the positive electrode lead inside the electrode element and the length of the negative electrode lead inside the electrode element is greater than 1/2(35[ mm ]) the height of the electrode element, the warping of the battery can be suppressed.

Next, a change in energy density according to the position of the extraction electrode lead is explained. Fig. 21A shows the outline of the cross section of the battery 21. The positive electrode lead 16 and the negative electrode lead 17 are connected to the electrode element (wound electrode element) 10 having an electrode element width W. As described above, the one-sided foil-foil structure (1) having a portion where the collector exposed surface of the one-sided application portion on the outer peripheral portion of either one of the positive electrode and the negative electrode and the collector of the other electrode face each other with the insulator (separator) therebetween and the one-sided foil-foil structure (2) having a portion where the collector exposed surface sides of the one-sided application portions on the outer peripheral sides of the positive electrode and the negative electrode face each other improve safety at the time of nailing compared with the normal structure.

There are portions of the exposed surface of the current collector disposed at the outer peripheral portion of the electrode on both outer surfaces of the wound battery. In the portion where the exposed surfaces of the current collectors are opposed to each other, when the electrode is viewed from the inner peripheral portion toward the outer peripheral portion (toward the winding direction), a length from a starting position (referred to as a starting position) of the foil to the foil opposed portion in the width direction of the electrode element to a position (referred to as a first bending position) of a corner of the bent portion of the electrode element in the width direction is defined as X, and when the electrode is viewed from the inner peripheral portion toward the outer peripheral portion (toward the winding direction), a length from a position (referred to as a second bending position) of the corner of the bent portion of the electrode element in the width direction to an end position (referred to as an end position) of the foil to the foil opposed portion in the width direction of the electrode element is defined as Y, the relationship X.gtoreq.Y. In the single-sided foil-foil structure (2), there are portions where the exposed surface of the foil and the foil on the other electrode face each other on both surfaces of the battery. In a portion where the exposed surface of the foil and the surface of the foil face each other, a length from a position of a start of the foil in a width direction of the electrode element to a corner of the foil opposing portion (referred to as a start position) to a corner of the bent portion in the width direction of the electrode element (referred to as a first bent position) when the electrode is viewed from the inner peripheral portion toward the outer peripheral portion (toward the winding direction) is defined as X, and a length from a position of a corner of the bent portion in the width direction of the electrode element (referred to as a second bent position) to an end position of the foil in the width direction of the electrode element to the foil opposing portion (referred to as an end position) when the electrode is viewed from the inner peripheral portion toward the outer peripheral portion (toward the winding direction) is defined as Y, the. Note that when only one corner of the bent portion exists, the first bent position and the second bent position are the same position, but when a plurality of corners of the bent portion exist, the position of the first bent portion in the electrode element is the first bent position when the electrode is viewed from the inner peripheral portion toward the outer peripheral portion, and the position of the last bent portion in the electrode element is the second bent position when the electrode is viewed from the inner peripheral portion toward the outer peripheral portion.

In FIG. 21B, the starting position of the foil to foil opposing portion is represented by X_RShowing that the first bending position is represented by X_LIndicating that the second bending position is Y_LShowing foil-to-foil relativeThe end position of the branch is represented by Y_RAnd (4) showing. A position P in the width direction of the electrode member where the positive electrode lead 16 exists is defined_CL(at X)_LPosition of side) and P_CR(at X)_RThe position of the side). Also, a position P in the width direction of the electrode element of the negative electrode lead 17 is defined_ALAnd P_AR. The coordinates of these positions are in mm]It is shown that the midpoint of the width W of the electrode member is used as 0, and the left side (X) thereof_L) Used as-and the right side (XR) thereof as +. The energy density can be increased by disposing the position in the width direction of the electrode elements of the positive electrode lead 16 and the negative electrode lead 17 between XR and YR.

Table 1 above includes "P_CL”、“P_CR”、“P_AL”、“P_AR"," width of electrode element ", and" X_L”、“X_R”、“X”、“Y_L”、“Y_RAnd "Y" data. For example, example 19 is an example in which the lengths of the positive electrode lead 16 and the negative electrode lead 17 inside the electrode element are each 20[ mm ]]Of less than 70[ mm ] of the electrode member]Half the height of (a). In addition, setting up (P)_CL＝-14[mm]、P_CR＝-10[mm]、P_AL＝-6[mm]，P_AR＝-2[mm]The width of the electrode element is 60[ mm ]]，X_L＝-30[mm]、X_R＝0[mm]、X＝30[mm]、Y_L＝-30[mm]、Y_R＝-16[mm]And Y is 14[ mm ]]). Therefore, it suffices that the positions in the electrode element width direction of the positive electrode lead 16 and the negative electrode lead 17 are X_RAnd Y_RThe condition in (a) to (b). In example 19, the energy density was 558[ Wh/L]The safety is highest (nail penetration permissible voltage: 4.50V).

Example 20 differs from example 19 in that only the position of the lead line is changed. Specifically, setting (P)_CL＝-14[mm]，P_CR＝-10[mm]，P_AL＝10[mm]，P_AR＝14[mm]The width of the electrode element is 60[ mm ]]，X_L＝-30[mm]，X_R＝0[mm]，X＝30[mm]，Y_L＝-30[mm]，Y_R＝-16[mm]And Y is 14[ mm ]]). In this case, from X_RObservation, negative electrode lead17 is located at and Y_RThe opposite side. Therefore, the position in the width direction of the electrode element of the positive electrode lead 16 and the negative electrode lead 17 is not satisfied at X_RAnd Y_RThe condition in (a) to (b). In example 20, the energy density is 548[ Wh/L]Smaller than in example 19.

As shown by comparison between example 19 and example 20, when the position in the width direction of the electrode member of the lead wire is satisfied at X_RAnd Y_RIn (b), the energy density increases.

As described above, in the embodiments of the present technology, the amount of warping of the battery is suppressed, and the energy density is further improved. Note that since the exposed portion of the current collector exists at the innermost circumference portion by about half to one turn, the position of the electrode lead connected to the exposed portion can be freely set. Further, since the thickness of the electrode element is not changed when the length of the electrode lead within the electrode element is increased, the problem of lower energy density does not arise.

Next, the position, the kind of material, and the like of the protective tape (coating material) in the present technology were examined. Note that the coating material includes a substrate. Further, the adhesive may be provided on one major surface of the substrate of the coating material, although this is not required. As described above, in the present technology, the reason why safety can be improved by providing the foil to the foil opposing portion at the outer peripheral portion of the battery is expected to be because a low-resistance short circuit occurs from the start of nail penetration, and the amount of heat generation at the portions where the electrode application portions oppose each other is reduced. In order to prevent short circuits due to cutting burrs on the current collector or the like, the foil-to-foil opposing portion may be provided with a coating material in place in addition to the separator. Since the separator is generally made of a porous material and shrinks while generating heat, the separator is less likely to be a cause of suppressing a short circuit of the foil-to-foil opposing portion. However, as for the coating material, it is suggested that when a material which is difficult to melt at the time of heat generation or a material having a large thickness is used, short circuit of the foil to the foil opposing portion is suppressed. Therefore, for various kinds of adhesive tapes to be used as a coating material, the case of suppressing short circuits has been examined. The results are provided below.

The OCV defect rate in Table 2 is defined as follows.

(definition of OCV Defect Rate)

After assembling the battery, the battery was first charged and then placed in a fully charged state for three days. Open Circuit Voltages (OCV) of the batteries after and before the standing for three days were compared, a voltage drop of 0.05V or more was counted as defective, and a ratio of the number of defective batteries to 100 assembled batteries was defined as an OCV defective rate.

The method of measuring the melting point of the base material of the protective tape is as follows.

(method of measuring melting Point)

Melting point of tape base was measured by Differential Scanning Calorimetry (DSC). The measurement was performed by cutting a 5mg test piece having a thickness of 0.1mm to fit the shape of the measurement container, enclosing the test piece in calorimetry, raising the temperature at 10 ℃/minute, measuring the DSC curve, obtaining the temperature at the peak of the melting point of the base on the DSC curve as the melting point. In this process, a-alumina powder is enclosed in different containers and used as a reference, the amount of a-alumina powder being about the same as the volume of the sample.

The outline of examples and comparative examples in table 2 is as follows.

< examples 21 to 24>

In examples 21 to 24, wound electrode elements having the cross-sectional structure shown in fig. 11 were used. The tape 18c at the positive electrode outer peripheral portion was similar to that in example 10, and as shown in table 2, the thickness of the tape 18b at the negative electrode inner peripheral portion was changed.

< examples 25 to 27>

In examples 25 to 27, a wound electrode member having a cross-sectional structure shown in fig. 11 was used. In positive electrode outer peripheral portion tape 18c, similarly to that in example 10, as shown in table 2, the material type in negative electrode inner peripheral portion tape 18b was changed.

< examples 28 to 31>

In examples 28 to 31, wound electrode elements having the cross-sectional structure shown in fig. 22 were used. In this wound electrode element, at the central portion of the battery at the inner periphery, a coating material (positive electrode inner peripheral portion tape) 18a and a coating material (negative electrode inner peripheral portion tape) 18b are opposed to each other with a separator therebetween.

< example 32>

In example 32, a wound electrode element having the cross-sectional structure shown in fig. 23 was used. The wound electrode element has a structure in which the positive electrode current collector 11a, which does not use an active material, does not reach the central portion of the battery.

< examples 33 and 34, comparative examples 12 to 14>

In examples 33 and 34 and comparative examples 12 to 14, wound electrode elements having the cross-sectional structure shown in fig. 11 were used. The negative electrode inner peripheral tape 18b was made of PET (polyethylene terephthalate) of 15 μm, and the thickness of the positive electrode outer peripheral tape 18c was changed as shown in table 2.

< examples 35 to 38>

A wound electrode member having a cross-sectional structure shown in fig. 11 is used. Examples 35 to 37 are examples in which there is a negative electrode inner peripheral portion tape 18b or a positive electrode outer peripheral portion tape 18c, in which there is only a negative electrode inner peripheral portion tape 18b, or in which there are no negative electrode inner peripheral portion tape 18b and positive electrode outer peripheral portion tape 18 c.

< example 39>

The positions of the positive electrode and the negative electrode in the wound electrode element of example 10 were replaced with each other, and the resulting structure was used as the wound electrode element of example 39 (not shown).

[ results of examples and comparative examples shown in Table 2]

Examples 21 to 31 shown in table 2 are examples in which the thickness and material of the outer peripheral tape are constant while the base type and thickness of the inner peripheral tape are varied. A certain law is derived from the results of examples 21 to 31.

Specifically, it has been found that when the product of the melting point (. degree. C.) of the tape base between the current collectors and the thickness (mm) of the substrate is less than 14.0 (. degree. C. mm), this part functions as a foil-to-foil opposing part, and when the product is not less than 14.0 (. degree. C. mm), this part does not function as a foil-to-foil opposing part. It is estimated from the following fact indicated by the comparison that the foil-to-foil opposing portion at the inner peripheral portion loses its function as a low-resistance short-circuit portion: in examples 23, 24, and 26 in which the product is not less than 14.0(° c-mm), and in example 32 in which there is no foil-to-foil opposing portion at the inner periphery, the nail penetration allowing voltages are the same. It is considered that the product of the melting point (. degree. C.) and the thickness (mm) of the substrate is associated with the coating material being easily melted, and when the product is larger, the coating material substrate is not easily melted. If the product of the melting point (. degree. C.) of the substrate and the thickness (mm) of the substrate is large, it is estimated that the coating material, which does not melt even in the case of heat generation, hinders short-circuiting between the foils, which reduces safety at the time of nail penetration.

Note that, since the drop of the nail penetration permitting voltage is as small as 0.05V even when there is a foil-to-foil opposing portion on the inner peripheral portion, and since the nail penetration permitting voltage is a sufficiently high value compared with the voltage of the normal structure shown in comparative example 5, in the embodiment of the present technology, the result does not indicate that it is indispensable that there is a foil-to-foil opposing portion on the inner peripheral portion.

Further, even in the case where Polyimide (PI) was used for the substrate (example 27), the nail penetration allowing voltage was equivalent to that in example 32, where PI is a high heat-resistant material whose melting point was not generally observed. Thus, it has been shown that the foil-to-foil opposite portion provided with the adhesive tape having the high heat-resistant substrate for which the melting point was not observed also lost its function as the foil-to-foil opposite portion.

Examples 33 and 34 and comparative examples 12, 13, and 14 are examples in which the thickness and material of the inner peripheral portion tape are unchanged when the base type and thickness of the outer peripheral portion are changed. A certain law is derived from the results of examples 33 and 34 and comparative examples 12, 13, and 14. Specifically, it has been found that when the product of the melting point (. degree. C.) of the tape base between the foils and the total thickness (mm) of the substrate is less than 4.6 (. degree. C. mm), this portion functions as a foil-to-foil opposing portion, and when the product is not less than 4.6 (. degree. C. mm), this portion does not function as a foil-to-foil opposing portion. The foil-to-foil opposing portion at the inner peripheral portion has lost its function as a low-resistance short-circuit member, estimated from the fact that: in comparative examples 12, 13, and 14 in which the product was not less than 4.6(° c. mm), and in comparative example 5 in which the foil-to-foil opposing portion was not present at the outer peripheral portion, the nail penetration allowing voltages were the same.

Note that it is not clear what the conditions that cause the foil-to-foil opposing portion to function as a low-resistance short-circuit portion are different between the inner peripheral portion and the outer peripheral portion. However, since the temperature of the nail tip is low at the start of nail penetration, it is estimated that the adhesive tape present on the foil-to-foil opposing portion of the outer peripheral portion needs to be more easily melted, otherwise it is difficult for a low-resistance short circuit to occur. As long as the foil-to-foil opposing portion satisfies the condition for use as a low-resistance short-circuit portion, the same adhesive tape, or adhesive tapes of different substrate types and thicknesses, may be used in the inner peripheral portion and the outer peripheral portion.

The function of the adhesive tape on the opposite part of the foil to the foil will now be described in detail. Basically, as described above, an adhesive tape is provided to prevent short-circuiting of the positive electrode and the negative electrode. Note that in the case where the foils of the foil-to-foil opposing portions are isolated from each other only by the separators, uneven portions of the electrolyte (if any) cause local unbalance of the voltage, which results in a state where the metal may precipitate. When the precipitation of metal breaks through the separator, the cell is shorted.

Examples 35 to 37 show various results when removing part or all of the protective tape from the foil onto the opposite part of the foil. The OCV defect rate was larger than that in example 10 in which the protective tape was not removed. Note that in addition to example 38, in the examples of the present technology and the comparative examples, a gel electrolyte was directly applied to the positive electrode and the negative electrode, so that an electrolyte was present in the battery. In this case, it was observed that there was no gel electrolyte in the foil-to-foil opposing portion, and during thermoforming, the electrolyte leaked from the electrode application portion to the foil-to-foil opposing portion, which resulted in the electrolyte being unevenly present in the foil-to-foil opposing portion as described above. As actually shown in example 38, when thermoforming was performed after the electrode member was inserted into the laminate, and then a sufficient amount of electrolyte was added to the laminate, the electrolyte was uniformly distributed on the foil-to-foil opposite portion, and the OCV defect rate was 0%. Therefore, the above mechanism can be logically explained.

Here, to summarize the conditions of providing and not providing the adhesive tape on the foil-to-foil opposing portion, even if the adhesive tape is not provided on the foil-to-foil opposing portion, the foil-to-foil opposing portion may cause a low resistance short circuit without causing problems such as OCV drop, depending on the battery manufacturing process. Furthermore, if an adhesive tape having a material and thickness that satisfy certain conditions is selected, the adhesive tape can be provided without inhibiting the function of a low-resistance short circuit of the foil to the foil opposing portion. Example 38 shows the result of fully immersing the foil-to-foil opposing portion in an electrolyte solution containing no polymer. However, the form of the electrolytic solution present here is not limited, and the electrolyte may be in the form of a gel electrolyte containing a polymer or the like.

Example 39 is an example in which the positions of the positive electrode and the negative electrode in example 10 are reversed. As shown in table 2, the same nail penetration permitting voltage as that in example 10 was obtained in example 39. The present technology proposes a structure obtained by basically starting winding with a separator alone, and then inserting electrodes in the order of a negative electrode and then a positive electrode. Note that the order of the positive electrode and the negative electrode is not limited, and a structure obtained by inserting the positive electrode after the separator and then winding with the negative electrode may be employed in the present technology.

(strengthening short circuits between foils in the innermost edges)

Depending on the state of the nail penetration, heat generation at a portion where a short circuit occurs between the foils may become large, which may cause the release of the short circuit, and a desired short circuit state may not be achieved. The short circuit between the foils refers to a short circuit of the aluminum foil (positive electrode collector 11a) and the copper foil (negative electrode collector 12a) at a low resistance. As the heat generation becomes larger, the aluminum foil may melt, and the short-circuit state of low resistance may be released. Aluminum foil is generally used for the collector of the positive electrode, and copper foil is often used for the collector of the negative electrode. In this case, since the aluminum foil has a low melting point, the release of the short circuit may occur. Therefore, the release of the short circuit can be suppressed by reinforcement with the positive electrode lead 16. Specifically, the positive electrode lead 16 may be provided at a portion where nail penetration safety is to be improved, thereby suppressing the release of short circuit and achieving higher safety. If it is assumed that the nail is stuck in the center of the battery, it is effective to use the structure as shown in 24A to 24C.

Fig. 24A, 24B, and 24C show external views of the battery 21 in which the positive electrode lead 16 and the negative electrode lead 17 are drawn from the external element 22. In general, as shown in fig. 24A, the positive electrode lead 16 and the negative electrode lead 17 are drawn from positions substantially symmetrical with respect to the center of the battery 21.

In contrast, as shown in fig. 24B, the position of the positive electrode lead 16 is near the center, and the length of insertion of the positive electrode lead 16 into the electrode element inside the external element 22 extends to near the center of the battery 21. As another configuration, as shown in fig. 24C, a rectangular region 16a is formed at the end of the portion of the positive electrode lead 16 of the electrode element inserted into the external element 22, and the rectangular region 16a is located near the center of the battery 21.

Further, an example configuration for suppressing the release of the short circuit is shown in fig. 25A to 25C. Fig. 25A shows an example of a cross-sectional structure of a wound electrode element (e.g., similar to fig. 23). In the wound electrode element as shown in the figure, a coating material (positive electrode inner peripheral portion tape) 18a and a coating material (negative electrode inner peripheral portion tape) 18b are opposed to each other with a separator therebetween at the center portion of the battery on the inner peripheral portion. In the example shown in fig. 25B, the foil on the innermost layer edge is coated with a conductive element 31. The conductive element 31 may be a foil or a conductive tape. The conductive member only needs to be electrically connected to the original collector foil, and the thickness of the conductive member is not limited. Further, the conductive member may be welded or fixed by an adhesive tape or the like as long as the conductive member is disposed at a desired position.

In the example shown in fig. 25C, the cut end of the foil at the innermost layer edge is folded back to form a folded-back portion 32. The folded back portion 32 may be over the entire width of the collector foil, or may be over a portion of the width. Further, the number of times of folding back is not particularly limited, and when the low-resistance short circuit may be released, it is effective to increase the number of times of folding back.

(integration of multiple cell elements from external elements)

In order to achieve a larger capacity, it is attempted to accommodate a plurality of battery elements in one external element. The battery having a larger capacity produced in this manner has a problem of reduced safety. Increasing the capacity in this way, security can be improved by applying the present technique. Specifically, in order to secure safety while keeping the reduction of energy density of a battery having a large capacity as small as possible, a structure in which elements having a single-sided foil-foil structure are stacked and inserted into one external element may be used.

Fig. 26A is a sectional view showing a cross section of a battery 40 having the following configuration: for example, two

wound electrode members

41A and 41B are accommodated in one outer member 42; fig. 26B is a sectional view showing a longitudinal section of the battery 40. A positive electrode lead 43A and a negative electrode lead 44A are drawn from the wound electrode element 41A, and a positive electrode lead 43B and a negative electrode lead 44B are drawn from the wound electrode element 41B. The positive electrode leads 43A and 43B are fixed externally by a thermoplastic resin and then connected together, and the negative electrode leads 44A and 44B are also connected together in a similar manner. The positive electrode current collectors located at the outermost peripheral portions of the

wound electrode members

41A and 41B are in contact with each other inside the external member 42.

The

wound electrode elements

41A and 41B are, for example, a second example of the winding structure of the present technology (single-sided foil-foil structure (2)) (refer to fig. 7). The single-sided foil-foil structure (2) is of the following structure: the foil collector exposed portion of the single-sided application portion of the positive electrode 11 faces the collector exposed portion of the single-sided application portion of the negative electrode 12, as shown in the broken line drawing. Specifically, the single-sided foil-foil structure (2) is a battery having portions opposing each other on the collector exposed surface sides of the single-sided application portions outside the windings of the positive and negative electrodes. When the number of layers in the case where one wound electrode member is housed in the exterior member 42 is represented by n, the number of layers of each of the

wound electrode members

41A and 41B is set to n/2, so that a capacity close to that of a battery cell is achieved. In the case where the number of original layers is not divisible by the number of stacked elements, the wound electrode elements to be inserted are set to have different numbers of layers, so that the following structure can be obtained: the multiple elements are integrated and minimize variations in electrode thickness and capacity from that of the galvanic cell. Table 3 shows the results of the experiment with 14 original layers. Note that the number of layers is obtained by counting the number of pairs of positive and negative electrodes in the thickness direction of the battery at the position of the negative electrode sheet.

In table 3, example 10 corresponds to example 10 in table 1. Examples 47 and 48 each show a case where the number of inserted cells (the number of wound electrode members) is 1. Comparative example 15 is an example of inserting one wound electrode element having a normal structure. In the case of using the single-sided foil-foil structure, the amount of reduction in safety when the capacity is increased (example 47) can be made smaller than that when the capacity is increased under the normal structure (comparative example 15). As the thickness of the element increases, higher security is achieved (example 48).

For example, in the case of a plurality of single-sided foil-foil structures (2) stacked and inserted in the external element as shown in fig. 7, the foil-to-foil opposing portion is located near the external element regardless of which surface the nail is inserted into. Therefore, since the safety mechanism of the wound foil structure (see paragraph [0052]) and the safety mechanism of the single-sided foil-foil structure (2) (see paragraph [0063]) are also maintained in the state in which the wound elements are stacked, it is considered that high safety is achieved (comparison between example 49 and comparative example 16).

When a large-capacity battery is formed of a single cell of a single-sided foil-foil structure (2), the foil thickness must be increased to obtain a result that the nail penetration permissible voltage is 4.2V, which results in a battery thickness of 6.8mm during charging. In contrast, when the battery was formed of a battery of two stacked batteries of the single-layer foil-foil structure (2), the result that the nail penetration permissible voltage was 4.3V could be obtained without increasing the foil thickness, and in this case, the battery thickness at the time of charging was 6.73 mm. This indicates that the use of the dual cell stack structure is more advantageous in terms of energy density (examples 48 and 49).

Further, as a result of an examination of the current flow at the time of nail penetration in the two-cell stack structure, it has been found that the amount of heat generation at the time of nail penetration start is small because the resistance between two cells is large. Since this is a method of connecting electrode leads, which determine the resistance between two batteries, safety is checked in different connection methods. As a result, it was found that the nail penetration allowable voltage was high because the resistance between the electrode leads was large.

Fig. 27A to 27E show a plurality of examples of the wire connecting method. Although the connection method of the positive electrode leads 43A and 43B is presented, the negative electrode leads 44A and 44B are connected similarly. Further, the resistance between the electrode leads is the resistance measured between the commonly connected positive electrode leads (43A and 43B) and the commonly connected negative electrode leads (44A and 44B).

The connection method of fig. 27A is a method of welding the root portions of the positive electrode leads 43A, 43B outside the external element 42. The negative electrode leads 44A, 44B are also connected similarly. This connection method is used in example 49.

The connection method of fig. 27B is a method of welding the entire

positive electrode lead

43A, 43B outside the external element 42. The negative electrode leads 44A, 44B are similarly connected. This connection method is used in example 50.

The connection method of fig. 27C is a method of welding the ends of the positive electrode leads 43A, 43B outside the external element 42. The negative electrode leads 44A, 44B are also connected similarly. This connection method is used in example 51.

The connection method of fig. 27D is a method of welding the ends of the positive electrode leads 43A, 43B outside the external element 42. The negative electrode leads 44A, 44B are similarly connected. Further, a separator 45 made of an insulator for isolating the

wound electrode members

41A and 41B is provided. This connection method is used in example 52. A comparison between examples 51 and 52 shows that this effect is also achieved when the elements are not electrically isolated from each other.

When the resistance between the leads is large, the resistance of the entire battery increases as viewed from the device side. According to the intended use, as shown in fig. 27E, it is effective to place a thermosensitive device 46 such as a Positive Temperature Coefficient (PTC) thermistor, which increases resistance only when current flows, between the negative electrode leads 44A and 44B. The negative electrode leads 44A and 44B are similarly connected. A connection method of placing a resistor is adopted in example 53, and a connection method of placing a PTC is adopted in example 54.

(description of "lead resistance between batteries (sum of positive electrode and negative electrode leads))

When the position shown by the black dot in fig. 28 is defined as the root of the electrode lead (for example, the positive electrode lead 43A) connected to the collector, the resistance between the roots of the positive electrode leads 43A and 43B of the two wound electrode elements (i.e., the resistance between the point a and the point B in fig. 28) is referred to as "the resistance between the leads on the positive electrode side". The resistance between the root portions of the electrode leads on the negative electrode side of the two wound electrode elements is referred to as "the resistance between the leads on the negative electrode side". The sum of the resistances between the leads on the positive electrode side and the negative electrode side is defined as "the lead resistance between the batteries (the sum of the positive electrode and the negative electrode leads)". Note that in fig. 28 and 29, when the two lead electrodes are pulled out from the external element, the thermoplastic resin 47 is provided to fill the gap between the lead electrodes and the external element and to seal the wound electrode element.

<3, application >

<3-1, example of Battery pack >

Fig. 30 is a block diagram showing an example circuit configuration of a case where a battery (hereinafter referred to as a secondary battery as appropriate) according to an embodiment of the present technology is applied to a battery pack. The battery pack includes an assembled battery 301, external elements, a switch unit 304 including a charge control switch 302a and a discharge control switch 303a, a current detection resistor 307, a temperature detection element 308, and a control unit 310.

Further, the battery pack includes a positive electrode terminal 321 and a negative electrode lead 322. During charging, the positive terminal 321 and the negative electrode lead 322 are connected to the positive terminal and the negative terminal of the charger, respectively, for charging. Further, during use of the electronic device, the positive electrode terminal 321 and the negative electrode lead 322 are connected to the positive electrode terminal and the negative electrode terminal of the electronic device, respectively, for discharge.

The assembled battery 301 includes a plurality of secondary batteries 301a connected in series and/or parallel. The secondary battery 301a is a second battery of the present technology. Note that although a case where 6 secondary batteries 301a are connected in 2 parallel and 3 series (2P3S) is shown in fig. 30, the batteries may be alternately connected in any manner such as n parallel and m series (n and m are integers).

The switching unit 304 includes a charge control switch 302a and a diode 302b, and a discharge control switch 303a and a diode 303b, and is controlled by the control unit 310. The diode 302b has a polarity opposite to the charging current flowing from the positive electrode terminal 321 in the direction of the assembled battery 301 and in the same direction as the discharging current flowing from the negative electrode lead 322 in the direction of the assembled battery 301. The diode 303b has the same polarity as the direction of the charging current and the opposite polarity to the discharging current. Note that, in the present example, the switch unit 304 is disposed on the + side, and the switch unit 304 may be disposed on the-side.

When the battery voltage reaches the overcharge detection voltage, the charge control switch 302a is turned off and controlled by the charge/discharge control unit so that the charge current does not flow through the current path of the assembled battery 301. When the charge control switch 302a is turned off, only the diode 302b can discharge. Further, when a large current flows during charging, the charging control switch 302a is turned off and controlled by the control unit 310, so that the charging current flowing through the current path of the assembled battery 301 is interrupted.

When the battery voltage reaches the overdischarge detection voltage, the discharge control switch 303a is turned off and controlled by the control unit 310 so that the discharge current does not flow through the current path of the assembled battery 301. When the discharge control switch 303a is turned off, only the diode 303b can be charged. Further, when a large current flows during discharge, the discharge control switch 303a is turned off and controlled by the control unit 310, so that the discharge current flowing through the current path of the assembled battery 301 is interrupted.

The temperature detection element 308 is, for example, a thermistor that is provided near the assembled battery 301 and is configured to measure the temperature of the assembled battery 301 and supply the measured temperature to the control unit 310. The voltage detection unit 311 measures the voltage of each secondary battery 301a constituting the assembled battery 301, performs a/D conversion of the measured voltage, and supplies the conversion result to the control unit 310. The current measuring unit 313 measures the current using the current detecting resistor 307, and supplies the measured current to the control unit 310.

The switch control unit 314 controls the charge control switch 302a and the discharge control switch 303a of the switch unit 304 based on the voltage and current input from the voltage detection unit 311 and the current measurement unit 313. When the voltage of any of the secondary batteries 301a has become the overcharge detection voltage or has become the overdischarge detection voltage or less, or when a large current suddenly flows, the switch control unit 314 transmits a control signal to the switch unit 304 to prevent overcharge, overdischarge, or overcurrent charge/discharge.

Here, for example, in the case where the secondary battery is a lithium ion secondary battery, the overcharge detection voltage is set to, for example, 4.20V ± 0.05V, and the overdischarge detection voltage is set to, for example, 2.4V ± 0.1V.

For the charge/discharge switch, a semiconductor switch such as a MOSFET may be used. In this case, parasitic diodes of the MOSFETs are used as the

diodes

302b and 303 b. When a P-channel FET is used for the charge/discharge switch, the switch control unit 314 supplies control signals DO and CO to the gates of the charge control switch 302a and the discharge control switch 303a, respectively. When the charge control switch 302a and the discharge control switch 303a are of a P-channel type, the charge control switch 302a and the discharge control switch 303a are turned on by a gate potential lower than a source potential by a predetermined value or more. Specifically, in the normal charging and discharging operations, the control signals CO and DO are set to the low level, and the charging control switch 302a and the discharging control switch 303a are in the on state.

Then, in the case of overcharge or overdischarge, for example, the control signals CO and DO are set to a high level, and the charge control switch 302a and the discharge control switch 303a are in an off state.

The memory 317 is constituted by, for example, a RAM or a ROM such as an Erasable Programmable Read Only Memory (EPROM) as a nonvolatile memory. The memory 317 stores in advance the numerical values calculated by the control unit 310, the internal resistance of the battery in the initial state of the secondary battery 301a measured during the manufacturing process, and the like, and is also rewritable as necessary. Further, the full charge capacity of the secondary battery 301a may be stored so that, for example, the remaining battery level may be calculated by the control unit 310.

The temperature detection unit 318 measures the temperature using the temperature detection element 308 to perform charge/discharge control under abnormal rise in temperature or to perform correction when calculating the remaining battery power.

<3-2 examples of Power storage System and the like >

The battery according to the embodiments of the present technology described above may be mounted on or used to supply power to apparatuses such as electronic devices, electric vehicles, and power storage devices.

Examples of the electronic device include a laptop personal computer, a smart phone, a tablet terminal, a Personal Digital Assistant (PDA), a mobile phone, a wearable terminal, a cordless cell phone, a video movie, a digital camera, an electronic book, an electronic dictionary, a music player, a radio, an earphone, a game machine, a navigation system, a memory card, a pacemaker, a hearing aid, an electric tool, an electric shaver, a refrigerator, an air conditioner, a television, a stereo, a water heater, a microwave oven, a dishwasher, a washing machine, a dryer, a lighting device, a toy, a medical device, a robot, a load regulator, and a traffic light.

Further, examples of the electric vehicle include a railway vehicle, a golf cart, an electric cart, and an electric car (including a hybrid car), and a battery is used as a driving power source or an auxiliary power source thereof.

Examples of the power storage device include a power source of a power storage unit of a building such as a house or a power generation facility.

Hereinafter, among the above-described application programs, a specific example of a power storage system using a power storage device to which the above-described battery of the present technology is applied is described.

An example of the configuration of the power storage system is as follows. The first power storage system is a power storage system in which a power storage device is charged by a generator configured to generate power from a renewable energy source. The second power storage system is a power storage system that includes a power storage device and is configured to supply power to an electronic device connected to the power storage device. The third power storage system is an electronic device that receives power from the power storage device. These power storage systems are embodied as systems that efficiently supply power in conjunction with an external power supply network.

Further, the fourth power storage system is an electric vehicle including: a converter configured to receive electric power from the electric power storage device and convert the electric power into driving force of the vehicle; and a control device configured to execute information processing related to vehicle control based on the information about the power storage device. The fifth power storage system is a power system including a power information transmission/reception unit (for transmitting/receiving a signal to/from another device via a network) for performing charging/discharging control of the above-described power storage device based on information received by the transmission/reception unit. The sixth power storage system is a power system that receives power from the power storage device and supplies power to the power storage device from a generator or a power grid. The power storage system is explained below.

<3-2-1, electric power storage System for Home application >

Referring to fig. 31, an example in which the power storage device having the battery of the present technology is applied to a home power storage system is described. For example, in the power storage system 100 of the home 101, power is supplied from the central power supply system 102 such as the thermal power generation 102a, the nuclear power generation 102b, and the hydroelectric power generation 102c to the power storage device 103 through the power grid 109, the information network 112, the smart meter 107, and the power hub 108. Further, the power storage device 103 is supplied with power from an independent power source such as the home generator 104. The supplied electric power is stored in the electric power storage device 103. With the electric power storage device 103, electric power to be used in the home 101 is fed to the home 101. A power storage system similar to that described above can be used not only in the home 101 but also in an office building.

A power generator 104, a power consumption apparatus 105, a power storage device 103, a control device 110 that controls each device, a smart meter 107, and a sensor 111 that acquires various information are provided in the home 101. These devices are connected to an information network 112 through a power grid 109. A solar cell, a fuel cell, or the like is used as the generator 104, and the electric power generated thereby is supplied to the electric power consumption device 105 and/or the electric power storage apparatus 103. The power consumption devices 105 include a refrigerator 105a, an air conditioner 105b, a television set 105c as a television receiver, a bathroom 105d, and the like. Further, the power consumption device 105 also includes an electric vehicle 106. The electric vehicle 106 includes an electric automobile 106a, a hybrid vehicle 106b, and an electric motorcycle 106 c.

The battery of the present technology is applied to the power storage device 103. For example, the battery of the present technology may be constituted by the above-described lithium ion secondary battery. The smart meter 107 has a function of measuring the consumption of commercial power and transmitting the measured consumption to the power company. The power grid 109 may be any one or combination of a dc power source, an ac power source, and a contactless power source.

Examples of the various sensors 111 include a human body sensor, an illuminance sensor, an object detection sensor, a power consumption sensor, a vibration sensor, a contact sensor, a temperature sensor, and an infrared sensor. Information acquired by the various sensors 111 is transmitted to the control device 110. Obtaining weather conditions, human conditions, etc. from the information from the sensors 111 allows automatic control of the power consuming equipment 105 to minimize energy consumption. Further, the control device 110 may transmit information about the home 101 to an external power company or the like via the internet.

The power hub 108 performs processing such as branching of power lines or DC-AC conversion. Examples of the communication method of the information network 112 connected to the control device 110 include a method using a communication interface such as a universal asynchronous receiver/transmitter (UART), and a method using a sensor network according to a radio communication standard such as bluetooth (registered trademark), ZigBee (registered trademark), or Wi-Fi (registered trademark). The bluetooth (registered trademark) method is suitable for multimedia communication, and communication can be achieved by one-to-many connection. ZigBee (registered trademark) uses the physical layer of IEEE (institute of electrical and electronics engineers) 802.15.4. Ieee802.15.4 is the name of a short-range wireless network standard called Personal Area Network (PAN) or wireless (W) PAN.

The control device 110 is connected to an external server 113. The server 113 may be controlled by any one of the home 101, the electric power company, and the service provider. The information to be transmitted and received by the server 113 is, for example, power consumption information, life pattern information, power cost, weather information, natural disaster information, and information related to power transaction. The information may be transmitted/received to/from a power consumption device (e.g., a television receiver) in the home, or may be transmitted/received from a device (e.g., a mobile phone) outside the home. Information may be displayed on a device having a display function, such as a television receiver, a mobile phone, a Personal Digital Assistant (PDA), or the like.

The control device 110 for controlling the respective units includes a Central Processing Unit (CPU), a Random Access Memory (RAM), a Read Only Memory (ROM), and the like, and is stored in the power storage device 103 in this example. The control device 110 is connected to the power storage device 103, the home generator 104, the power consumption equipment 105, various sensors 111, and the server 113 via the information network 112, and has functions of adjusting commercial power consumption and power generation, for example. Note that the control device 110 may also have other functions such as a function of performing electric power transaction in the electric power market.

As described above, not only the electric power from the centralized power supply system 102 such as the thermal power generation 102a, the nuclear power generation 102b, the hydraulic power generation 102c, and the like, but also the electric power (photovoltaic power generation, wind power generation) generated by the household power generator 104 may be stored in the electric power storage device 103. Therefore, even if the amount of electric power generated by the home generator 104 fluctuates, it is possible to perform control, for example, to make the amount of electric power transmitted to the outside constant or discharge a necessary amount of electric power. For example, it is possible to use electric power in such a manner that electric power obtained by photovoltaic power generation is stored in the electric power storage device 103, midnight electric power at a lower price is stored in the electric power storage device 103, and the electric power stored in the electric power storage device 103 is discharged for daytime use at a higher power cost.

Note that, in this example, an example has been described in which the control device 110 is stored in the power storage device 103; however, the control device 110 may be stored in the smart meter 107, or may be a single unit. Further, the power storage system 100 may be used for a plurality of households in a plurality of residences or a plurality of independent houses.

<3-2-2, application of Power storage System to vehicle >

Referring to fig. 32, an example of applying the present technology to an electric power storage system of a vehicle is described. Fig. 32 schematically shows an example of the configuration of a hybrid vehicle employing a series hybrid system to which the present technology is applied. A series hybrid system is a vehicle that uses electric power generated by a generator driven by an engine or electric power obtained by temporarily storing generated electric power in a battery and is driven by an electric power/driving force converter.

The hybrid vehicle 200 is mounted with an engine 201, a generator 202, an electric power/driving force conversion device 203,

drive wheels

204a, 204b, wheels 205a, wheels 205b, a battery 208, a vehicle control device 209, various sensors 210, and a charging port 211. The battery of the present technology described above is applied to the battery 208.

The hybrid vehicle 200 runs using the electric power/driving force conversion device 203 as a power source. An example of the driving force conversion device 203 is a motor. The electric power/drive power conversion device 203 is activated by electric power from the battery 208, and torque of the electric power/drive power conversion device 203 is transmitted to the

drive wheels

204a and 204 b. Note that DC-AC conversion or reverse conversion (AC-DC conversion) may be used as necessary, so that the power/drive power conversion device 203 may be applied to either one of an AC motor and a DC motor. Various sensors 210 control the engine speed via the vehicle control 209 and control the opening of a throttle valve (not shown) (throttle position). The various sensors 210 include a speed sensor, an acceleration sensor, an engine speed sensor, and the like.

The torque of the engine 201 is transmitted to the generator 202, and the power generated by the generator 202 according to the torque may be stored in the battery 208.

When the hybrid vehicle 200 is decelerated by a brake mechanism, not shown, resistance at the time of deceleration is applied as torque to the electric power/driving force conversion device 203, and regenerative electric power generated by the electric power/driving force conversion device 203 is stored in the battery 208 according to the torque.

The battery 208 may also be connected to an external power source of the hybrid vehicle 200 so as to receive electric power from the external power source through the charging port 211 as an inlet and store the received electric power.

Although not shown, an information processing device for processing information on vehicle control based on information on the secondary battery may be provided. Such an information processing apparatus may be an information processing apparatus that indicates a remaining battery level based on information about the remaining battery level.

Note that an example of a series hybrid vehicle that uses electric power generated by a generator driven by an engine or electric power obtained by temporarily storing generated electric power in a battery and is driven by a motor has been described above. However, the present technology is also effectively applied to a parallel hybrid vehicle that uses power output from an engine and a motor as a drive source and switches between three modes of driving by only the engine, driving by only the motor, and driving by the engine and the motor. Further, the present technology can also be effectively applied to a so-called electric vehicle that is driven only by a drive motor without using an engine.

<4, modification >

Although the embodiment of the present technology is specifically described above, the present technology is not limited to the above-described embodiment, but various modifications may be made based on the technical idea of the present technology. For example, the configurations, methods, procedures, forms, materials, numerical values, and the like illustrated in the above embodiments are merely examples, and configurations, methods, procedures, forms, materials, numerical values, and the like different therefrom may be used as necessary.

Note that the present technology may also have the following configuration.

(1) A battery comprising a wound electrode element, wherein the wound electrode element is wound around a positive electrode and a negative electrode sandwiching a separator,

wherein the positive electrode has a first exposed surface that is formed with a positive electrode active material layer on one surface of a positive electrode collector and is not formed with a positive electrode active material layer on the other surface of the positive electrode collector within an outer peripheral portion of the wound electrode element;

the negative electrode has a second exposed surface that is in an outer peripheral portion of the wound electrode element, that is formed with a negative electrode active material layer on one surface of a negative electrode current collector, and that is not formed with a negative electrode active material layer on the other surface of the negative electrode current collector; and

the first exposed surface and the second exposed surface are opposed across the separator.

(2) The battery according to (1), wherein a first coating material is provided on at least a part of the first exposed surface or the second exposed surface in an outer peripheral portion of the wound electrode element.

(3) The battery according to (1) or (2),

wherein the first coating material has at least a first substrate, and

the product of the melting point of the first substrate and the thickness of the first substrate is less than 4.6[ ° c-mm ].

(4) The battery according to the above-mentioned (1),

wherein the positive electrode has a third exposed surface in an inner peripheral portion of the wound electrode element, the third exposed surface being free from the positive electrode active material layer formed on at least one face of the positive electrode collector,

the negative electrode has a fourth exposed surface in an inner peripheral portion of the wound electrode element, the fourth exposed surface being free from the negative electrode active material layer formed on at least one surface of the negative electrode current collector, and

the third exposed face and the fourth exposed face are opposed with the separator therebetween.

(5) The battery of (4), wherein a second coating material is disposed on at least a portion of the third exposed surface or the fourth exposed surface.

(6) The battery according to the above-mentioned (5),

wherein the second coating material has at least a second substrate, and

the product of the melting point of the second substrate and the thickness of the second substrate is less than 14.0[ ° c-mm ].

(7) The battery according to the above-mentioned (1),

wherein opposing portions of the first exposed surface and the second exposed surface opposing each other include curved portions, and

when a length from a position in an electrode element width direction of a start portion of the opposing portion to a position in the electrode element width direction of a corner of the bent portion is defined as X, and a length from the position in the electrode element width direction of the corner of the bent portion to a position in the electrode element width direction of a terminal portion of the opposing portion is defined as Y, when viewed in a winding direction, a relationship is satisfied

X≥Y。

(8) The battery according to the above-mentioned (1),

wherein the battery includes an external element, and

the outer element is a composite film.

(9) The battery according to the above-mentioned (1),

wherein the positive electrode and the negative electrode each have an electrode lead, and

at least one electrode lead inside the wound electrode element has a length greater than half of a height of the wound electrode element.

(10) The battery according to the above-mentioned (1),

wherein the positive electrode and the negative electrode each have an electrode lead,

the facing portions of the first and second exposed surfaces facing each other include curved portions,

at least one electrode lead is positioned such that a position of the at least one electrode lead in the width direction of the electrode member is located between a position of one end of the opposing portion in the width direction of the electrode member and a position of the other end of the opposing portion in the width direction of the electrode member.

(11) A battery comprising a wound electrode element, wherein the wound electrode element is wound around a positive electrode and a negative electrode sandwiching a separator,

the positive electrode has a first exposed surface that is in an outer peripheral portion of the wound electrode element, a positive electrode active material layer is formed on one surface of a positive electrode collector, and no positive electrode active material layer is formed on the other surface of the positive electrode collector, and

the first exposed surface is opposed to a region on both surfaces of the negative electrode current collector, on which the negative electrode active material layer is not provided, across the separator.

(12) A battery comprising a wound electrode element, wherein the wound electrode element is wound around a positive electrode and a negative electrode sandwiching a separator,

wherein the negative electrode has a second exposed surface that is in an outer peripheral portion of the wound electrode element, a negative electrode active material layer is formed on one surface of a negative electrode current collector, and a negative electrode active material layer is not formed on the other surface of the negative electrode current collector, and

the second exposed surface is opposed to a region on both surfaces of the positive electrode collector, on which the positive electrode active material layer is not provided, across the separator.

(13) A battery pack, comprising:

the battery according to (1);

a control unit configured to control the battery; and

an external element comprising a battery.

(14) An electronic device configured to receive power from the battery according to (1).

(15) An electric vehicle comprising:

the battery according to (1);

a conversion device configured to receive electric power from the battery and convert the electric power into driving force of the vehicle; and

a control device configured to perform information processing regarding vehicle control based on the information regarding the battery.

(16) A power storage device comprising the battery according to (1) and configured to supply power to an electronic device connected to the battery.

(17) The power storage device according to (16),

further comprising a power information control device configured to transmit or receive a signal to or from another device via a network,

wherein the power storage device performs charge/discharge control of the battery based on the information received by the power information control device.

(18) A power system that receives power from the battery according to (1).

(19) The power system according to (18), wherein the power is supplied to the battery from a generator or a power grid.

List of reference numerals

10 wound electrode element

11 positive electrode

11a Positive electrode collector

11b Positive electrode active Material containing coating film

12 negative electrode

12a negative electrode current collector

12b negative electrode active material containing coating film

15 separator

16 positive electrode lead

17 negative electrode lead

21 nonaqueous electrolyte battery

22 external elements.

Claims

1. A battery comprising a wound electrode element, wherein the wound electrode element is wound around a positive electrode and a negative electrode sandwiching a separator,

the first exposed face and the second exposed face are opposed across the separator;

an opposing portion of the first exposed surface and the second exposed surface opposing each other includes a curved portion; and

when a length from a position in an electrode element width direction of a start of the opposing portion to a position in the electrode element width direction of a corner of the bent portion is defined as X, and a length from a position in the electrode element width direction of the corner of the bent portion to a position in the electrode element width direction of a terminal end of the opposing portion is defined as Y, when viewed toward a winding direction, a relationship is satisfied

X≥Y。

2. The battery of claim 1, wherein a first coating material is disposed on at least a portion of the first exposed surface or the second exposed surface within an outer peripheral portion of the wound electrode element.

3. The battery according to claim 2, wherein the battery further comprises a battery cell,

wherein the first coating material has at least a first substrate; and

the product of the melting point of the first substrate and the thickness of the first substrate is less than 4.6 ℃. mm.

4. The battery as set forth in claim 1, wherein,

wherein the positive electrode has a third exposed surface in an inner peripheral portion of the wound electrode element, the third exposed surface being free from the positive electrode active material layer formed on at least one face of the positive electrode current collector;

the negative electrode has a fourth exposed surface within an inner peripheral portion of the wound electrode element, the fourth exposed surface being free from the negative electrode active material layer formed on at least one face of the negative electrode current collector; and

the third exposed face and the fourth exposed face are opposed, and the separator is interposed between the third exposed face and the fourth exposed face.

5. The battery of claim 4, wherein a second coating material is disposed on at least a portion of the third exposed surface or the fourth exposed surface.

6. The battery pack as set forth in claim 5,

wherein the second coating material has at least a second substrate; and

the product of the melting point of the second substrate and the thickness of the second substrate is less than 14.0 ℃. mm.

7. The battery as set forth in claim 1, wherein,

wherein the battery comprises an external element; and

the outer element is a composite film.

8. The battery as set forth in claim 1, wherein,

wherein the positive electrode and the negative electrode each have an electrode lead; and

9. The battery as set forth in claim 1, wherein,

wherein the positive electrode and the negative electrode each have an electrode lead;

opposite portions of the first exposed surface and the second exposed surface opposite to each other include curved portions;

10. A battery comprising a wound electrode element, wherein the wound electrode element is wound around a positive electrode and a negative electrode with a separator interposed therebetween, wherein the negative electrode has a second exposed surface that is within an outer peripheral portion of the wound electrode element;

the positive electrode has a first exposed surface that is formed with a positive electrode active material layer on one surface of a positive electrode collector and is not formed with a positive electrode active material layer on the other surface of the positive electrode collector, within an outer peripheral portion of the wound electrode element; and

the first exposed surface is opposed to a region where the negative electrode active material layer is not provided on both surfaces of the negative electrode current collector across the separator, and an opposed portion where the first exposed surface and the second exposed surface are opposed to each other includes a curved portion; and

X≥Y。

11. A battery comprising a wound electrode element, wherein the wound electrode element is wound around a positive electrode and a negative electrode with a separator interposed therebetween, wherein the positive electrode has a first exposed surface that is within an outer peripheral portion of the wound electrode element,

wherein the negative electrode has a second exposed surface that is in an outer peripheral portion of the wound electrode element, a negative electrode active material layer is formed on one surface of a negative electrode current collector, and no negative electrode active material layer is formed on the other surface of the negative electrode current collector; and

the second exposed face is opposed to a region on both surfaces of the positive electrode collector on which the positive electrode active material layer is not provided across the separator,

X≥Y。

12. A battery pack, comprising:

the battery of claim 1;

a control unit configured to control the battery; and

an external element comprising the battery.

13. An electronic device configured to receive a supply of power from the battery of claim 1.

14. An electric vehicle comprising:

the battery of claim 1;

a conversion device configured to receive electric power from the battery and convert the electric power into driving force of a vehicle; and

15. A power storage device comprising the battery of claim 1 and configured to provide power to an electronic device connected to the battery.

16. The power storage device according to claim 15,

further comprising a power information control device configured to transmit or receive a signal to or from another device via a network;

17. A power system receiving a supply of power from the battery of claim 1.

18. The power system of claim 17, wherein the power is supplied to the battery from a generator or a power grid.